Sampler Device for Radioactive Spent Resins/Sludge

I can't give you a recommendation other than you will need to furnish a great deal more detailed information in order to obtain a valid reply. I assume that you are talking about spent ion exchange resin as well as corrosion products and such removed during treatment of (presumably) nuclear power plant condensate/fluids/other waste. A full 9m dia x 7m high tank would contain a huge amount of radwaste. Spent ion exchange resins could be deadly "hot".

How much of a sample? How accessible is the tank with respect to radiation hazard. How deep must you probe for your sample. Etc., etc.